In processing a substrate such as a semiconductor wafer or the like, many processes to supply a process gas under a predetermined reduced pressure atmosphere are used. In many cases, such a process is performed while placing a substrate in a process chamber which can maintain a reduced pressure atmosphere. Processing a substrate generally includes a plurality of processes, and a plurality of process chambers for performing those processes are connected to a substrate conveyance chamber and the substrate is carried into a process chamber and carried out of the process chamber by a conveyance mechanism such as a robot so as to be conveyed to another process chamber.
In such a substrate processing apparatus, it is general that a plurality of process chambers and a load-lock chamber are arranged around a conveyance chamber, and a robot in the conveyance chamber conveys a substrate via an arm. The load-lock chamber is a pressure adjusting chamber provided for carrying a substrate in the conveyance chamber or carrying a substrate out of the conveyance chamber. That is, since the conveyance chamber is connected to the process chambers, inside the conveyance chamber must be maintained under a reduced pressure atmosphere close to an environment inside the process chambers. Thus, it is so constructed to isolate a space inside the conveyance chamber by providing the load-lock chamber.
Although various processes are applied to a substrate, there may be a case in which a process time in each process differs greatly. In order to raise a throughput of substrate processing, it is preferable that the process time required for each process is almost equal. Therefore, in order to process substrates of the same number of sheets for the same process time, it is general to provide a plurality of process chambers to perform concurrently for a process taking a long process time. That is, it is preferable to adjust a number of substrates being processed per unit time is the same for each process.
FIG. 1 is a plan view showing an example of a conventional substrate processing apparatus provided with a plurality of process chambers for performing the same process. The substrate processing apparatus shown in FIG. 1 comprises a load-lock chamber 2, a conveyance chamber 4 connected to one side of the load-lock chamber 2 and six process chambers 6 connected to remaining three sides of the load-lock chamber 2.
The load-lock chamber 2 is capable of accommodating two sheets of substrate at the same time. Two transfer robots 8 for carrying the substrates into the load-lock chamber 2 or carrying the substrates out of the load-lock chamber 2 are installed in the vicinity of the load-lock chamber 2.
The interior of the conveyance chamber 4 connected to the load-lock chamber 2 is capable of being maintained at a reduced pressure environment, and when the load-lock chamber 2 is set to the predetermined reduced pressure environment (degree of vacuum), the rotating-type transfer robot 10 in the conveyance chamber 4 picks up and holds substrates in the load-lock chamber 2, and conveys the substrates to the process chamber 6.
The transfer robot 10 has two arms and is capable of transferring two substrates simultaneously. Therefore, two sets of process chamber 6 are connected to the conveyance chamber 4 in a state where the two sets are arranged side by side so that two sheets of substrate held by the two arms are carried into the two process chambers, respectively, at the same time.
A total of six sets of process chamber 6 of which two each are connected to the three sides of the conveyance chamber 4 other than the side to which the load-lock chamber 2 is connected, respectively, so as to reduce a process time per one sheet of substrate in the process step by performing the process by the six sets of process chamber 6.
It is also suggested to provide a transfer mechanism having arms to hold substrates and capable of linearly moving within the conveyance chamber 4 instead of the above-mentioned rotating type transfer robot.
Moreover, there is also suggested a method of conveying substrates from a load-lock chamber to a process chamber by a conveyance case having a transfer mechanism (for example, refer to Patent Documents 1 and 2). In this method, there is no need to arrange a transfer robot in a conveyance chamber, and a number of process chambers is not limited by the transfer robot and the configuration of the conveyance chamber, thereby enabling a reduction in an installation area of an entire substrate processing apparatus.
The following patent documents disclose techniques relating to prior art of the present invention.
(Patent Document 1) Japanese Laid-Open Patent Application No. 3-184331
(Patent Document 2) Japanese Laid-Open Patent Application No. 6-97258
In the above-mentioned substrate processing apparatus shown in FIG. 1, since it is necessary to arrange the process chambers and the load-lock chamber to surround the conveyance chamber, there is a limit in the number of process chambers that can be arranged. In the example shown in FIG. 1, the number of process chambers connectable to the conveyance chamber 4 is six at the maximum.
Although the number of sides to which the process chambers are connectable is increased by making the configuration of the conveyance chamber to be a polygonal shape of more than hexagon, one side may be smaller than a size of the process chamber, and, as a result, the process chamber cannot be connected.
Thus, there is a limit in the number of process chambers that can be provided to the conventional substrate processing apparatus, and there is a problem in that it cannot deal with a process to continuously performing many steps or a process to concurrently perform a large amount of processes each having one or plurality of steps.
When a transfer mechanism of a movable type such as a linear-type conveyance mechanism instead of the rotating-type transfer robot, the restriction in the number of process chambers due to the configuration of the conveyance chamber is eliminated. However, since the transfer mechanism moves in the conveyance chamber which is to be maintained at a vacuum and clean atmosphere, the transfer mechanism may be a generation source of particles. Especially, there is a problem in that particles may be generated by a cable for supplying electric power to the transfer mechanism being drawn, which is a cause of pollution of substrates.
Moreover, if the number of process chambers is increased, a space of the conveyance chamber is also increased, and there is a problem in that a pump having a large exhaust capacity is needed to maintain such as large space under a reduced pressure environment, which increases a cost. Further, there also is a problem in the entire apparatus is enlarged by enlargement of the conveyance chamber, which results in an increase in an area occupied by the apparatus.
The present invention was made in view of the above-mentioned problems, and an object of the present invention is to provide a substrate processing apparatus which can convey substrates to a plurality of process chambers while maintaining an atmosphere of substrates to be processes at a predetermined environment and reduce an installation area of the entire apparatus.